The present invention relates to hydraulic shock absorbers for motor vehicles, for example, including snowmobiles. More specifically, the present invention relates to motor vehicle hydraulic shock absorbers that because of their design and construction are adapted for facile and relatively inexpensive manufacture while affording real time, selectively variable damping characteristics.
Shock absorbers are commonly used in vehicle suspension systems to absorb unwanted vibrations that occur during driving. Specifically, shock absorbers are generally connected between the body (sprung mass) and the suspension (unsprung mass) of the vehicle to dampen the vibrations transmitted from the suspension to the body.
Motor vehicle shock absorbers usually have a hollow cylinder defining an internal chamber or cavity that is filled with fluid and that is divided into working compartments (viz., a compression compartment and a rebound compartment) by a piston assembly slidably positioned in the internal chamber. The compression and rebound compartments are usually in fluid communication with a reservoir compartment. Shock absorbers also usually include internal valving that permits fluid to flow between the compression, rebound and reservoir compartments as the piston assembly moves within the internal chamber.
One end of the shock absorber cylinder is closed and is typically connected to the vehicle suspension by a suitable linkage. A piston rod extends through a seal assembly mounted in the other end of the cylinder. The piston rod has its inner end connected to the piston assembly and its outer end connected to the vehicle body by a suitable connector.
A shock absorber usually also includes a compression valve, a replenishing valve and valving in the piston assembly to control or restrict the flow of damping fluid within the shock absorber during the compression and extension strokes of the shock absorber, thereby providing a damping force, which xe2x80x9csmoothsxe2x80x9d or xe2x80x9cdampensxe2x80x9d vibrations transmitted from the suspension to the body. The damping characteristics of a shock absorber are determined by the fluid pressure differential across the piston assembly required to drive the fluid between the compression, rebound and reservoir compartments. This pressure differential and the resulting flow rate, in turn, control the speed at which the piston assembly may move in the cylinder responsive to the external forces applied to the shock absorber. The greater the degree to which the flow of damping fluid is restricted, the greater the damping forces that are provided by the shock absorber. Accordingly, a xe2x80x9csoftxe2x80x9d compression and rebound stroke is afforded when the flow of damping fluid between the working compartments is relatively unrestricted. By contrast, a xe2x80x9cfirmxe2x80x9d compression and rebound stroke is afforded when there is an increased restriction in the flow of fluid between the working compartments.
Different desired driving characteristics, such as ride comfort, vehicle handling, and vehicle ground holding ability, depend on the amount of damping force provided by the motor vehicle""s shock absorbers. The amount of damping force required to meet a particular set of driving characteristics is, in turn, dependent on driving surface conditions including, for instance, the terrain over which the vehicle travels, and the manner in which a vehicle is being driven. Because driving conditions and desired characteristics may change, often even within the scope of a single journey, the damping force required to meet the desired driving characteristics needs also to change often. This is particularly so when the vehicle being driven is a snowmobile.
A need has long existed for a motor vehicle shock absorber that provides for selective real-time damping characteristics in response to changing driving conditions and/or changes in desired driving xe2x80x9cfeel.xe2x80x9d Additionally, a need also exists for such a shock absorber that additionally may be reliably mass-produced on a relatively inexpensive basis.
Accordingly, it is an object of the present invention to provide an improved motor vehicle shock absorber that permits selective, real-time adjustment of the shock absorber damping characteristics.
Another object of the present invention is to provide an improved shock absorber of the type described that may be used in rugged, changeable driving conditions, such as those frequently encountered by a snowmobile, and that may be reliable and relatively inexpensively mass-produced.
Still another object of the present invention is to provide an improved shock absorber, as described, where a novel solenoid subassembly, which is part of a novel end cap assembly, is utilized to selectively and variably control the force required to unseat the shock absorber""s compression valve, which is part of a novel compression head assembly, during movement of the piston assembly in the compression stroke direction or motion. A related object of the present invention is to provide an improved shock absorber, as described, where the design and construction of the novel end cap and compression head assemblies enable these assemblies to be separately manufactured, as sub-assemblies, and to be relatively inexpensively assembled together, in the shock absorber manufacturing facility.
The foregoing objects are met, in whole or in part, by the improved shock absorber of the present invention that includes novel compression head and end cap assemblies, and that provides desired changeable damping force characteristics through selective, real-time adjustable damping by using a solenoid subassembly, which is part of the novel end cap assembly, to variably control the force required to unseat the compression valve, which is a part of the novel end cap assembly and which is clamped against a valve seat on the novel compression head assembly, during movement of the shock absorber""s piston assembly in the compression stroke direction. The design and construction of the novel compression head assembly and the novel end cap assembly facilitates their expeditious and sure assembly, as components of the shock absorber. Fluid flow past the compression valve during the compression stroke of the piston assembly is selectively controlled in a real-time adjustable manner by a solenoid subassembly, which is used to apply a selectively variable valve closure force to the compression valve, thereby regulating fluid flow between the compression compartment and the reservoir compartment during the compression stroke. The valve closure force applied by the solenoid subassembly may be controlled directly by the vehicle operator, or optionally by an autonomous shock absorption control system. Through the use of the present invention, shock absorption damping may be selectively adjusted in real-time in response to changing driving conditions or changes in desired driving characteristics. The advantages of real-time adjustable damping include increased safety and rider comfort.
These and other objects, advantages and benefits of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment of the present invention with reference to the accompanying drawings.